Method and means for operating cracking coil installations



Aug. 9, 1932- E. w. LUSTER 1,870,855

METHOD AND MEANS FOR OPERATING CRACKING COIL INSTALLATIONS Filed Sept. 25. 192

M M W 6% (7% INVENTOR ATZI'ORNEY v Patented Aug. 9,1932

UNITED STATES PATENT OFFICE ERIC W.,LUSTER, 0F WESTFIELD, NEW JERSEY, ASSIGNOR TO STANDARD OIL DEVELOP MENT COMPANY, A CORPORATION OF DELAWARE HETHOD AND MEANS FOR OPERATING CRACKING COIL INSTALLATIONS Application filed September 25, 1929. Serial No. 394,959.

This invention relates to improvements in the operation of installations for cracking hydrocarbon oil, particularly those of the type involving a series connected coil, digestion chamber or soaking drum, expansion or separatin chamber, and rectification means. A particu ar object of the invention is to secure a highly etficicnt utilization of the heat of the cracked roduct, simultaneously regulating the quality of the tar produced in the cracking operation, and minimizing coke formation in the separating chamber. In a preferred form of the invention, the desired result is obtained by passing at least a port-ion of the feed oil into the exit line from the soaking drum and/0r into the upper portion.

of the separating zone.

The invention will be fully understood from the following description, read in connection with the accompanying drawing, in which the figure is a side elevation, partly in section.

In the drawing, reference numeral 1 denotes a cracking coil furnace setting in which there is a radiant heat section 2 and a convection heat section 3. Pipe coils 5 and 3 are arranged in these sections, respectively. The radiant heat section of the coil discharges through a line 6 into the lower part of a soaking drum 7. The product from the soaking drum passes from near its top through a line 8 into the lower part of a separator 9. A pressure control valve 10 is installed in line 8. The separator has bafiies 11 in the upper part, and a draw-ofi line 12 from the bottom leading to a tar'cooler 13.

Vapors from the separator pass through line 14 into an intermediate point of rectification means such as a primary bubble tower 15. This has the usual bell cap plates 16 or.

equivalent vapor-liquid contact devices. Va-

pors from the primary bubble tower pass through a line 17 to a secondary bubble tower 18. Vapors from this latter pass through a line 19 to a condensing coil 20.

A line 21 serves for the passage of condensate formed in the bottom of tower 15 to the coil 5 in the radiant heat section 2 of the cracking coil furnace setting. A pump 22 is installed in this line. A line 23, in which there is a pump 24, conveys condensate from this source also, through a bypass 25, to line 8 leading from the soaking drum. Line 23 is connected by a branch 26 to the upper part of separator 9.- Valves 27 and 28 are installed respectively in the lines 25 and 26.

I prefer to supply the feed oil to the system through a line 29 via heat exchange coils 30 and 31 in the vapor spaceof towers 18 and 15 respectively. The oil from the heat exchange coils fiows through a line 32 to a preheater 33 arranged in the convection heat section of the cracking coil setting 1 in such manner that the exit gases pass over the preheater. A line 34 connects it with an intermediate point of bubble tower 15.

A line 35 is connected to the bottom of tower 18 for the removal of condensate oil formed in it. Suitable means, not shown, are provided for receiving the oil from this line and also from the condensing coil 20.

In the operation of the system described, the feed oil, which may be gas oil, reduced crude, or any other suitable stock, is passed through line 29, heat exchange coils 30, 31, preheater33, and into tower 15. COIIlblHQd feed oil and condensateare drawn off from the bottom of this tower through line 21 into section 5 of the cracking coil,from which it passes through section 4 and into soaking drum 7.

Simultaneously combined feed oil and condensate are drawn from the bottom of tower 15 and passedv through lines 23 and 25, and 23 and 26', into the vapor line 8 and the separator 9 respectively. This oil is .in part vaporized and the vapors carry into tower 15 a large part of the available heat, which they impart to the feed oil entering through line 34. The amounts of oil passing through connections 25 and 26 are adjusted proper degree of cooling to thecracked product coming from the soaking drum, to secure the required dilution of the tar separated in 9, and to minimize coke formation in the upper part of the separator. cracking occurs in the separator.

While I do not wish to be limited to any precise conditions of operation, the followmg example is given to indicate the general to give the No substantial regulation of flow: To a coil handling 10,000

gallons per hour of total feed, 4,000 to 6,000

gallons of oil are recycled per hour to the separator. The temperature of the recycled .oil will be from 615 to 680 F.

About 25% of the Qll SO recycled is discharged on baflle plates 11 in the upper part 4 of separator 9, to wash out coke particles and to condense heavy coke-forming constituents which would otherwise be carried into tower 15. The remaining of the oil is discharged into line 8 and serves primarily to control tar temperature and gravity.

The method described gives two points of intimate contact between the cracked product and the added oil. The heat of the cracked product is accordingly utilized very efiiciently. The valves 25 and 28 may be regulated to secure the desired flow of relatively cool oil into the soaking drum outlet and separator. These valves will usually each be open at least in part. Under special conditions one only may be used, the other being closed.

The conditions of operation for the coil, drum and towers do not form an essential part of the present invention. By way of example only, it may be stated that the cracking coil is run at a temperature of about 840 to 950 F. at a' pressure of 350 to 1,000 lbs. per square inch. The temperature in the soaking drum may be from 780 to 900 F. and at a pressure not substantially less than that in the coil. The pressure in the separator 9 may be reduced to 60 to 100 lbs. per square inch or less, and the bubble towers 15 and 18 may be run under atmospheric or other pressure as desired.

The foregoing description is merely illustrative and various changes may be made within the scope of the appended claims in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. Method of cracking hydrocarbon oil which comprises introducing the oil to be cracked into an intermediate stage of a rectifying zone, drawing off commingled feed oil and condensate from said zone, passing the mixture of oil so formed into a cracking zone, discharging the oil therefrom into a separating zone in which no substantial cracking takes place introducing into the stream of oil passing to the separating zone a quantityof commingled feed oil and condensate from the rectifying zone, and also introducing a quantity of such oil into the upper part of the separating zone, and passing vapors from the cracked product, together with vapors from the feed oil, into the rectification zone at a point below that at which the feed oil enters.

2. Apparatus for cracking hydrocarbon oil comprising cracking equipment, a separator receiving the cracked product therefrom,

a rectifyingtower into which the vapors of the separator.

ERIC W. LUSTER. 

